Ok, so we went to Fantasy only on Friday evening (the men's night). As for our first time, it was very nice. What we didn't like:
• there was definitely too much cigarette smoke in the bar area. I mean much too much.
• the "singles" supposedly permitted only with "careful selection" included several - let me say - not exactly carefully selected guys that didn't add to the overall feel.
What we liked:
• there were lots of interesting people, always ready to play
• everyone was kind and respected barriers
• as for our first time we enjoyed a nice swap with a German couple
• good snacks
• acceptable prices for drinks
As for the entrance price - it's quite high (about 60 euro), but we don't feel it was money badly spent.
Overall we liked it and we've already decided to visit Prague and Fantasy again, this time being a bit more courageous.